UPDATE 1-Energy customer losses worsen for SSE and Scottish Power

* SSE says 2017/18 earnings per share to be lower than last year (Recasts and updates with Scottish Power figures, adds details, background)

By Karolin Schaps

LONDON, July 20 (Reuters) - SSE, Britain's second-biggest energy supplier, and rival Scottish Power announced further customer losses on Thursday, underscoring the increasingly competitive nature of an energy retail market that has attracted dozens of new entrants.

SSE said it had lost another 230,000 customer accounts in the three months to the end of June, reducing the total to 7.7 million at the end of its financial first quarter.

This compares with a loss of 210,000 customer accounts over the year to March 2017, showing that customer losses are deepening for the number two supplier.

Rival Scottish Power, owned by Spain's Iberdrola, also said on Thursday it had lost more customers, with 35,000 leaving over the first half of the year. Total customer accounts have fallen to 5.285 million, a spokesman said.

Britain has attracted a series of new energy suppliers by making it easier for newcomers to enter the market, with more than 50 suppliers now offering electricity and gas to households.

New entrants have been welcomed by British energy users, disappointed by years of rising bills and often poor customer service, resulting in a record number of households switching supplier in March.

The government has tried to encourage consumers to consider switching supplier rather than remaining on more expensive deals once initial offers have expired.

Britain's "Big Six" legacy energy suppliers, which include SSE and Scottish Power, also face pressure from the government to act to reduce their most expensive tariffs.

Last year the competition watchdog found that households overpaid 1.4 billion pounds a year between 2012 and 2015 because of uncompetitive standard tariffs many consumers are placed on.

Earlier this month, energy regulator Ofgem proposed to cap bills for some of the most vulnerable energy customers and to make it easier to switch supplier.

In response, SSE said in its results update on Thursday that competition should be at the heart of the market and that it therefore offers a wide range of tariffs, products and services.

The utility also reiterated that earnings per share for the full financial year were likely to be lower than last year but said it was on track to pay a higher dividend to shareholders. (Editing by Greg Mahlich/Keith Weir)